Drug-Resistant Melanoma Finding May Improve Treatment Approach

Scientists have discovered how
cancer develops resistance against a new melanoma treatment from
Roche Holding AG (ROG), a finding that could help extend lives of some
patients.

Roche’s Zelboraf, a so-called BRAF inhibitor, works by
blocking a protein that fuels tumor growth in about half of
patients with advanced forms of the skin cancer. Zelboraf,
cleared for sale in the U.S. in August, eventually stops working
as the cancer spurs production of a different version of the
protein that the drug is designed to block, researchers found.

While the Roche medicine worked better at prolonging
survival and shrinking tumors than chemotherapy, patients
develop a resistance to the therapy within a year, said David
Solit, an author of the study. Knowing how the cancer fights
back could help fuel new therapies and, in particular, a
combination approach to extend life, much like HIV/AIDS
medicines, Solit said.

“They have this dramatic response to the treatment, but
then after six or nine months, the tumor progresses on the
drug,” Solit, an associate member and attending physician at
Memorial Sloan-Kettering Cancer Center in New York, said in an
interview. “People have been pretty interested in figuring out
why the resistance develops, so that’s what we’ve been looking
into.”

“It’s possible that you could develop either a combination
of drugs or simply a single drug, a different RAF inhibitor,
that would be resistant to this mechanism and therefore could
have a longer duration of activity,” Solit said.

More than 68,000 Americans were diagnosed with melanoma
last year, according to the National Cancer Institute. The five-
year survival rate is 15 percent among patients diagnosed after
the cancer has spread. When caught in its early stages, the
disease has a 98 percent survival rate after five years.